Compressor assembly for air conditioner system

ABSTRACT

An air conditioning system includes a compressor assembly having a housing and a valve. The housing generally encloses a discharge chamber and a suction chamber. The valve is operative for controlling the pressure differential between the discharge and suction chambers. The valve includes a body, a ball, spring, flange and a piston. The body has a first passage and a second passage in fluid communication with the first passage. The piston is slidably coupled to the body for axial movement between a closed position and an open position. The piston includes a hole for supporting the ball therein for movement with the piston between the closed position, wherein the ball engages the body to prevent fluid flow between the first and second passages, and the open position, wherein the ball is spaced apart from the body to allow fluid flow between the first and second passages. The ball is fixedly secured to the piston to prevent erosion due to relative movement and contact between the ball and the piston

REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application No. 60/751,100 filed Dec. 16, 2005 and 60/777,422 filed on Feb. 27, 2006, which are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The invention relates to air conditioning or heat pump systems. More particularly, the invention relates to a compressor assembly for use in an air conditioning or heat pump system.

BACKGROUND OF THE INVENTION

In an air conditioning or heat pump system having a hermetic compressor, condenser, evaporator and expansion device, a problem exists when the condenser fan fails, functions intermittently, or when the condenser surface is restricted so that adequate air flow across the surface does not allow the refrigerant to condense to liquid. As a result, the gas returns to the compressor at a much higher pressure/temperature than under normal operating conditions. The compressor continues to run, thereby re-compressing the gas to an even higher pressure/temperature and creating a high pressure safety condition.

To circumvent this issue a pressure relief valve is typically used between the discharge chamber and the suction chamber (inside a hermetic shell) of the compressor. The pressure relief valve opens when the differential pressure exceeds a predetermined nominal value, e.g. less than the burst pressure of the hermetic shell. As the compressor continues to run, the internal temperature rises until a thermal overload circuit located in the compressor motor windings trips and disconnects the electrical circuit. This causes the compressor to shut-down until the temperature of the motor windings falls below a reset point of the overload. As this point is reached the compressor restarts and the cycle begins again. Due to the complexity of the heat pump systems reversing the role of the evaporator and condenser, and/or the location of the thermal overload in the motor windings in relation to the pressure relief valve discharge ports, the relief valve may be kept open by the flow of liquid, or vapor and liquid, or cool vapor refrigerant causing insufficient temperature rise in the motor windings to trip the thermal overload.

In conventional pressure relief valves utilizing a ball/piston interface, a clearance fit is provided between the ball and the piston for ease of assembly. However under the conditions discussed above when refrigerant is being pumped through the relief valve holding the valve wide open, the ball is free to spin in a socket form in the piston. Under continuous run conditions the spinning of the ball erodes the piston at the socket. Test and field failure samples have shown that the ball will eventually erode into, or through the piston rendering the pressure relief valve inoperative, i.e. wide open, while permitting continuous compressor operation without providing any cooling.

Thus, it remains desirable to provide an air conditioning system with an improved compressor which overcomes the shortcomings of the aforementioned conventional air conditioning systems.

SUMMARY OF THE INVENTION

According to one aspect of the invention, a compressor assembly is provided for an air conditioning system. The compressor assembly includes a housing generally enclosing a discharge chamber and a suction chamber. The compressor assembly also includes a valve operative for controlling the pressure differential between the discharge and suction chambers. The valve includes a body, a piston, a spring and a ball. The body has a first passage and a second passage in fluid communication with the first passage. The piston is slidably coupled to the body for axial movement between a closed position and an open position. The spring continuously biases the piston toward the closed position. The ball is fixedly secured to the piston for movement therewith between the closed position, wherein the ball engages the body to prevent a fluid flow between the first and second passages, and the open position, wherein the ball is spaced apart from the body to allow the fluid flow between the first and second passages. The ball is fixedly secured to the piston to prevent erosion due to relative movement and contact between the ball and the piston.

According to another aspect of the invention, an air conditioning system includes a condenser, an expansion valve, an evaporator and a compressor assembly. The compressor assembly includes a housing and a pressure relief valve. The housing generally encloses a discharge chamber and a suction chamber. The valve is operative for controlling the pressure differential between the discharge and suction chambers. The valve includes a body, a ball and a piston. The body has a first passage and a second passage in fluid communication with the first passage. The piston is slidably coupled to the body for axial movement between a closed position and an open position. The piston is continuously biased toward the closed position. The piston includes a hole for supporting the ball therein for movement with the piston between the closed position, wherein the ball engages the body to prevent fluid flow between the first and second passages, and the open position, wherein the ball is spaced apart from the body to allow fluid flow between the first and second passages. The ball is fixedly secured to the piston to prevent erosion due to relative movement and contact between the ball and the piston.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic view of an air conditioning system according to the invention;

FIG. 2 is a cross sectional view of a compressor assembly of the air conditioning system according the invention;

FIG. 3 is an enlarged cross sectional view of the compressor assembly of FIG. 2;

FIG. 4 is a cross sectional view of a valve in the compressor assembly of FIG. 3 shown in the open position; and

FIG. 5 is a cross sectional view of the valve in the closed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an air conditioning system for cooling the air in a generally enclosed environment is generally indicated at 2. The system includes a compressor 4, a condenser 6, an expansion device 14 and an evaporator 16. The compressor 4 compresses a refrigerant gas to high pressure, which causes the gas to become hot. The hot high pressure gas exits the compressor 4 and enters the condenser 6, where it dissipates heat and condenses into a high pressure liquid. The liquid moves from the condenser 6 to an expansion device 14 via a liquid line 12. Optionally, the liquid filters through a filter drier 13 prior to entering the expansion device 14. The liquid passes through the expansion device 14 and into the evaporator 16, where it evaporates to a vapor or gas state. Heat is absorbed from the air surrounding the evaporator due to the evaporation process, thereby cooling the enclosed environment. The gas returns to the compressor 4 via a suction line 18 to begin another refrigeration cycle.

Referring now to FIGS. 2-3, the compressor 4 includes a high-pressure discharge chamber 3 and a low-pressure suction chamber 5. The compressor 4 in the illustrated embodiment is a scroll compressor, which utilizes a pair of spiral-shaped scrolls 7, 9 fit together to form generally crescent-shaped gas pockets. One of the scrolls is a fixed scroll 7 and remains stationary, while the other is an orbiting scroll 9 that moves in a spiral manner about the fixed scroll 7. The orbiting scroll 9 is driven by an internal motor 11 via a crankshaft 15. Gas from the suction chamber 5 is drawn into an outer pocket created by the two scrolls 7, 9. As the spiral motion continues, the gas is forced toward the center of the fixed scroll 7. The volume of the pocket becomes continuously smaller toward the center, thereby compressing the gas. When the compressed gas reaches the center of the fixed scroll 7, it is discharged into the discharge chamber 3 and recirculated in the refrigeration cycle as described above. Optionally, other types of compressors may be used, such as a reciprocating piston-type compressor.

A channel 17 is formed in the fixed scroll 7 and extends between the discharge chamber 3 and the suction chamber 5. A pressure relief valve 10 is threaded into the channel 17 of the fixed scroll 7. The valve 10 may also be fixedly secured to the fixed scroll 7 by welding, or other suitable fixing methods. The pressure relief valve 10 is movable between a closed position in FIG. 5 and an open position in FIG. 4 for regulating the pressure differential between the chambers 3, 5 during operation of the compressor 4.

The valve 10 includes a body 20, a piston 30, a biasing spring 40 and a ball 50. A cylindrical bore 22 extends through an end of the body 20 for slidably supporting the piston 30 therein. A first passage 24 extends through an opposite end of the body 20 and is coaxial with the bore 22 A second passage 26 extends through the body 20 along an axis generally orthogonal to the first passage 24.

The piston 30 includes a first hole 32 formed at one end and a second hole 34 formed at an opposite end. A center bore 35 extends axially between the first 32 and second 34 holes. The center bore 35 has a smaller diameter than both the first 32 and second 34 holes, thereby defining opposite and annular-shaped first and second end walls 36, 38.

The spring 40 is compressed between the first end wall 36 and a flange 39 formed near the opening of the bore 22 for continuously axially biasing the piston 30 toward the closed position shown in FIG. 5.

The ball 50 is fixedly secured to the piston 30 to prevent spinning of the ball 50 at the seat 49. More specifically, an annular lip or seat 49 is defined at the intersection between the walls of the center bore 35 and the second end wall 38. A portion of the ball 50 abuts the seat 49 and is press or interference fit in the second hole 34 of the piston 30. The interference fit prevents rotation of the ball 50 relative to the piston 30 as fluid passes through the passages 24, 26 when the valve is in the open position, as shown in FIGS. 2 and 4, thereby minimizing erosion or wear of the ball 50 and piston 40 surfaces.

In a second embodiment, the ball 50 is disposed in the second hole 34 and welded to the piston 30. The weld is achieved utilizing a high current density projection weld process. As in the previous embodiment, the weld prevents the ball 50 from rotating relative to the piston 30 as fluid passes through the passages 24, 26 when the valve is in the open position. Thus, the welding of the ball 50 to the piston 30 minimizes erosion or wear of the ball 50 and piston 40 surfaces.

In use, the ball 50 is maintained in the closed position due to the axial force applied by the spring 40 between the piston 30 and the flange 39 of the body 20. Fluid flow between the first 24 and second 26 channels is prevented by the ball 50 in the closed position. When the pressure in the first passage 24 exceeds a predetermined pressure level, generally determined by the spring constant of the spring 40, the piston 30 and ball 50 are displaced from the closed position toward the open position. Once the ball 50 is in the open position, fluid can pass between the first 24 and second 26 passages, thereby relieving pressure in the first passage 24. The ball 50 being fixedly secured in the second hole 34 of the piston 30 is prevented from spinning due to the flow of fluid passing between the first 24 and second 26 passages. Once the pressure is relieved, the spring 40 forces the piston 30 and ball 50 to the closed position to prevent further fluid flow between the passages 24, 26.

The invention has been described in an illustrative manner. It is, therefore, to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. For example, the air conditioning system described above may also be operated as a heat pump incorporating the compressor assembly and pressure relief valve as described herein. Thus, within the scope of the appended claims, the invention may be practiced other than as specifically described. 

1. A compressor assembly for an air conditioning system, said compressor assembly comprising: a housing generally enclosing a discharge chamber and a suction chamber; and a valve operative for controlling the pressure differential between the discharge and suction chambers, the valve having: a body having a first passage and a second passage in fluid communication with the first passage; a piston slidably coupled to the body for axial movement between a closed position and an open position; a spring continuously biasing the piston toward the closed position; and a ball movable with the piston between the closed position, wherein the ball engages the body to prevent fluid flow between the first and second passages, and the open position, wherein the ball is spaced apart from the body to allow fluid flow between the first and second passages, the ball being fixedly secured to the piston to prevent erosion due to relative movement and contact between the ball and the piston.
 2. A compressor assembly as set forth in claim 1, wherein the piston includes a generally cylindrical hole for supporting the ball therein.
 3. A compressor assembly as set forth in claim 2, wherein the ball is press fit in the hole to prevent the ball from spinning relative to the piston.
 4. A compressor assembly as set forth in claim 2, wherein the ball is disposed in the hole and welded to the piston.
 5. A compressor assembly as set forth in claim 4, wherein the weld is formed by a high current density projection weld.
 6. A compressor assembly as set forth in claim 2, wherein the piston includes a center bore having a smaller diameter than the hole, the center bore being substantially axially aligned with and adjacent to the hole to define an annular seat.
 7. A compressor assembly as set forth in claim 6, wherein the ball abuts the seat.
 8. A compressor assembly as set forth in claim 7, wherein the ball is disposed in the hole and welded to the piston.
 9. A compressor assembly as set forth in claim 9, wherein the weld is formed by a high current density projection weld.
 10. A compressor assembly as set forth in claim 7, wherein the ball is press fit in the hole to prevent the ball from spinning relative to the piston.
 11. A compressor assembly as set forth in claim 10, wherein the first and second passages are generally orthogonal relative to each other.
 12. A compressor assembly as set forth in claim 11, wherein the piston moves between the closed and open positions along an axis generally aligned with a longitudinal axis of one of the first and second passages.
 13. A compressor assembly as set forth in claim 12, wherein the ball in the closed position abuts an opening of the one of the first and second passages to prevent fluid flow between the first and second passages.
 14. A compressor assembly as set forth in claim 13, wherein the hole, center bore and the one of the first and second passages are generally coaxially aligned.
 15. An air conditioning system comprising: a condenser; an expansion device; an evaporator; and a compressor assembly having a housing and a pressure relief valve, the housing generally enclosing a discharge chamber and a suction chamber, the valve being operative for controlling the pressure differential between the discharge and suction chambers, the valve including: a body having a first passage and a second passage in fluid communication with the first passage; a ball; and a piston slidably coupled to the body for axial movement between a closed position and an open position, the piston being continuously biased toward the closed position, the piston having a hole for supporting the ball therein for movement with the piston between the closed position, wherein the ball engages the body to prevent fluid flow between the first and second passages, and the open position, wherein the ball is spaced apart from the body to allow fluid flow between the first and second passages, the ball being fixedly secured to the piston to prevent erosion due to relative movement and contact between the ball and the piston.
 16. A compressor assembly as set forth in claim 15, wherein the ball is press fit in the hole to prevent the ball from spinning relative to the piston.
 17. A compressor assembly as set forth in claim 15, wherein the ball is welded to the piston.
 18. A compressor assembly as set forth in claim 17, wherein the weld is formed by a high current density projection weld.
 19. A compressor assembly as set forth in claim 15, wherein the piston includes a center bore having a smaller diameter than the hole, the center bore being substantially axially aligned with and adjacent to the hole to define an annular seat.
 20. A compressor assembly as set forth in claim 19, wherein the ball abuts the seat and is press fit in the hole to prevent relative movement between the ball from and the piston.
 21. A compressor assembly as set forth in claim 19, wherein the ball abuts the seat and is welded to the piston to prevent relative movement between the ball from and the piston. 